1. Field of the Invention
The invention relates to protective circuits in general and more particularly to a testing arrangement in which the efficacy of a protective circuit can be tested.
2. Description of the Prior Art
Protective coupling circuits for connecting a modem or data set to a public switched network are known in the art. These circuits limit the output voltage applied to the network regardless of the value of the input voltage within a predetermined time. The circuits generally use a program or standard resistor which when connected to a regulated voltage supply provides a reference voltage which is used for operating the circuits. Circuits of this type have not in the past been provided with on-line testing arrangements by which an operator can determine the efficacy of the circuit. Generally, the circuits have been removed from the operative environment and bench tested to determine whether or not they are functioning properly. This arrangement is both costly and inconvenient since it generally requires substitution and later test. When difficulty occurs in a communication path which may include a large variety of equipment such as business machines, modems, data sets and switched network facilities, as well as the protective coupling devices, it is incumbent to readily determine which of the devices in the end-to-end connection are malfunctioning. Removal of a device with either substitution or bench testing is not a practical solution.